As described in French patent application No. 2,897,900 filed by the applicant, this type of engine includes a cylinder with a combustion chamber containing a fuel mixture.
This fuel mixture conventionally undergoes a compression stage by the piston of this engine, then a combustion stage. This combustion is performed under the effect of a spark ignition, such as a spark plug.
As described in this patent application, this fuel mixture can undergo an abnormal combustion due to a pre-ignition thereof before the mixture is ignited, by the spark plug for example.
This abnormal combustion, which is different from knocking combustion, generally occurs with engines, mainly highly supercharged engines, which have undergone a stage of capacity reduction referred to as downsizing. The purpose of this stage is to reduce the size and the capacity of the engine while keeping the same power and the same torque as conventional engines, which makes them likely to be subject to pre-ignition.
Thus, considering the high pressures and the high temperatures reached in the combustion chamber as a result of supercharging, an abnormal combustion start (or pre-ignition) can occur, generally sporadically, and sometimes well before ignition of the fuel mixture by the spark plug takes place. This notably occurs at high engine loads and low engine speeds.
If this fuel mixture pre-ignition causes a violent abnormal combustion, random and sporadic, it is referred to as rumble and it can generate very high pressure levels in the combustion chamber (above 100 bars). These pressure levels that go together with an increase in thermal transfers with the cylinder and the piston of the engine can cause partial or total destruction of the moving elements of the engine, and the engine can even run out of order.
The present invention therefore aims to overcome the aforementioned drawbacks by means of preventive action allowing to control, to limit or even to prevent pre-ignition of the fuel mixture.